Aiming to control various properties resulting from electron charge, spin, and phase

[Keio Spintronics Network - Ono Laboratory, Kyoto University] The Ono Laboratory is creating nanoscale artificial substances, by combining materials such as metals and semiconductors. The aim of this research is to control a diverse range of properties resulting from electron charge, spin, and phase.



Q."

What we’re focusing on especially is the interaction between electron spins and magnets. For example, we investigate how magnets react when we pass a current through them. We hope this will lead to new properties that can be utilized in devices."



To create artificial nano-substances, measurements must be made with a variety of instruments. In the Ono Lab, researchers fabricate multi-layer films, just a few atoms thick, using ultra-high vacuum deposition. They also fabricate nanoscale patterns using electron beam lithography.



Q."We create a vacuum, then we melt matarials, say, iron or gold, so atoms evaporate from the liquid surface. This equipment can make artificial substances by depositing those atoms on a substrate. In electron beam lithography, an electron beam is focused down to a nanometer, to form nanostructures by creating patterns on a substrate. This process is used to fabricate the semiconductor components used in ordinary computers."



In quantum mechanics, the extremely small size of particles results in measurement fluctuations called quantum noise. To investigate the mechanism behind this noise, the Ono Lab uses an apparatus called a dilution refrigerator. This measures quantum effects close to absolute zero, and measures the noise as well.



Q."We’re doing measurements at extremely low temperatures. For example, we measure the quantum interference effect, which occurs when electron degrees of freedom are confined to two dimensions. And we measure what happens to quantum mechanical noise, as in the tunnel magnetoresistance effect.

Device sensitivity is defined by signal-to-noise ratio. If we can understand the origin of the noise, and its mechanism, we could minimize that noise, and predict the limits on devices. So we think this is important research."



Microfabrication technology that can process substances with nanometer precision, and development of substances by controlling and combining elements at the atomic level… This type of spintronics research will form the basis for next-generation electronics materials. And in due course, it’s expected to play a role in daily life.



Q."The best thing about this research is that, by using nanotechnology, we can design an ideal setting for studying material properties, and do research based on our design, to find out what happens in that setting. Sometimes we get the results we expect, and sometimes, things happen that we didn’t expect at all. And the most enjoyable aspect of this research is that, by studying why the unexpected happens, it’s possible that we’ll discover new phenomena that haven’t even been thought of before."